KR20030069692A - Method of Manufacturing Lightweight Aggregate of Apatite Crystal Structure - Google Patents

Abstract

PURPOSE: A lightweight aggregate having an apatite crystal structure and its preparation method are provided, to prepare lightweight aggregate having excellent physical properties with low cost. CONSTITUTION: The method comprises the steps of mixing 40-60 wt% of the phosphate waste water sludge containing calcium, fluorine and phosphorus and capable of forming an apatite crystal, and 20-60 wt% of a stabilizer containing an enamel sludge containing feldspar; calcining the mixture at a temperature of 900-1,300 deg.C; and pulverizing the calcined one. Preferably the stabilizer comprises 5-15 wt% of enamel sludge; 5-15 wt% of the iron sludge containing calcium and iron; 5-15 wt% of clay; and 5-15 wt% of waste pearlite. Preferably the calcined one is pulverized to a size of 10 mm, 6 mm or 2 mm.

Description

Method of manufacturing lightweight aggregate having apatite crystals {Method of Manufacturing Lightweight Aggregate of Apatite Crystal Structure}

The present invention relates to a method for producing lightweight aggregates having apatite crystals, and more particularly, to a method for producing lightweight aggregates used in fillers and structures of artificial stones having apatite crystals using phosphate wastewater sludge as a raw material.

Until now, lightweight aggregates used in building and timber have been manufactured by mixing minerals such as volcanic stone, vermiculite, diatomaceous earth, and zeolite together with clay and firing them at high temperature. However, these raw materials have limited production sites, and resources are increasingly depleted, and thus remain a problem in the production of lightweight aggregate.

Korean Patent No. 0296261 (name of the invention: a dry material using phosphate wastewater sludge and a method for producing the same) discloses a method of manufacturing wet tiles and aggregates using sludge discharged from a phosphate process. According to the patent, when the sludge discharged from the phosphate process is heated to a high temperature, crystals of hydroxyapatite (10CaO · 3P ₂ O ₅ · OH) and fluoro apatite (10CaO · 3P ₂ O ₅ · F) are precipitated, which is heat resistant. This is an excellent component of the human body bones and teeth because it is excellent in affinity with the human body, but the absorption rate is large, there is a disadvantage that the compressive strength, tensile strength, bending strength falls. In order to improve this, clay, feldspar, feldspar, pottery, kaolin, clay, fly ash, silica, glaze sludge, etc. are added to prepare wet tiles and aggregates. In addition, these sludges are also used as raw materials for cement production, but if they contain phosphate components, the properties of the cement may be deteriorated. Until now, due to the problems described above, wastewater sludge having apatite crystals having excellent affinity with human bodies is not recycled, and most of them are landfilled.

In particular, since phosphate wastewater sludge contains calcium and phosphorus components, calcination at high temperature does not degas the fluorine ions contained in the wastewater sludge, but rather it is immobilized in the apatite crystal to form fluorite apatite. Since fluorine ions and calcium are slightly dissolved, they cannot be used in structures such as lightweight aggregates. Due to these characteristics, in order to manufacture products such as lightweight aggregates using components having apatite crystals, the components eluted in water must be suppressed, the absorption rate must be reduced, and the compressive strength must be increased.

The present invention has been made to solve the above-mentioned problems, an object of the present invention is to add an appropriate stabilizer to the wastewater treatment sludge containing phosphate and to heat to a high temperature of about 1200 ℃ or more using a rotary killer having excellent characteristics It is to manufacture lightweight aggregate.

In other words, the present inventors have studied and formulated suitable stabilizers to produce lightweight aggregates having excellent properties, and thus, methods for producing lightweight aggregates for construction and civil engineering having excellent suppression, absorption rate, compressive strength and hardness of elution components, and the like. We developed lightweight aggregates for building and civil engineering.

1A to 1E show X-ray diffraction diagrams of apatite crystals according to firing temperatures of phosphate wastewater sludge.

2 is a graph showing the weight loss and gas generation time generated during firing phosphate wastewater sludge.

Figure 3 is a graph showing the analysis results over time of harmful gases generated during calcination of phosphate wastewater sludge.

In the present invention to achieve the above object

Mixing from 20 to 60% by weight of a stabilizer comprising 40 to 60% by weight of phosphate wastewater sludge containing calcium, fluorine and phosphorus and glaze sludge containing feldspar, which can form apatite crystals;

Calcining the resulting mixture in a temperature range of 900 to 1300 ° C; And

It provides a method for producing a lightweight aggregate comprising the step of pulverizing the resulting fired product.

In particular, the stabilizer is based on the total amount of the mixture 5 to 15% by weight glaze sludge, 5 to 15% by weight of calcium and iron components, 5 to 15% by weight clay and 5 to 15 It is preferred to include by weight percent waste pearlite.

In addition, it is preferable to further perform the step of drying the mixture by using the waste heat of the rotary kill, and it is easy to use the pulverized product obtained through the firing after cooling to a size of 10mm, 6mm or 2mm.

Another object of the present invention is to provide a lightweight aggregate which is manufactured according to the above-described method, which is light, low in water absorption and high in compressive strength.

In the present invention, in detail, the wastewater discharged from a silicon wafer, a manufacturing plant of a liquid crystal display device, a semiconductor factory, or a coating factory that performs phosphate coating, and the like, is washed off after washing the surface of a substrate composed of silicon and SiO ₂ It is to provide a method for producing a lightweight aggregate used in the filler and the structure of artificial stone having apatite crystal using the sludge as a raw material.

Hereinafter, the present invention will be described in more detail.

There are various methods to induce weight reduction, but the lightweight aggregate produced in this patent forms glassy at high temperature to reduce the absorption rate, plays a foaming role, and forms Na ₂ SiF ₆ , K ₂ SiF ₆ crystals to form F ⁻ Glaze sludge consisting of feldspar was added to prevent elution of ions.

When lubricating glazes on porcelain or tiles, some of the glaze is attached to the porcelain and flows out, and the glaze that flows outward is collected and disposed of. These wastes are called glaze sludge, and because they melt at low temperatures, they lower the firing temperature during the production of lightweight aggregates, form glass, lower the absorption rate, and at the same time dissolve the fluorine in the phosphate sludge. To prevent it.

Glaze sludge is mostly composed of feldspar, and especially fluoride ions contained in apatite react with Na, K and Si elements in feldspar to form sodium fluoride and potassium fluoride. Through this, fluorine ions can be prevented from slowly eluting out of water.

Such glaze sludge is preferably added in the range of about 5-15% by weight, based on the total amount of the mixture. This is because if the added amount is less than 5% by weight, the effect of preventing the absorption rate and the dissolution of fluorine is insignificant, and if it exceeds 15% by weight, the melting temperature is too low, so it is not preferable because it is not melted and discharged in the rotary kill when firing. . More preferably, it is in the range of about 8 to 12% by weight.

Meanwhile, in order to plate zinc on steel products such as wires and pipes, it is necessary to remove rust and impurities adhering to the surface, and for this purpose, it is immersed in hydrochloric acid and sulfuric acid. At this time, when the concentration of acid is lowered, it is sent to a wastewater treatment plant for treatment, which is called steel sludge. The main component is iron and wastewater treatment calcium, which contains about 60% of iron and about 30% of calcium. . When steel sludge is added, oxygen generated as Fe ³⁺ ions in iron oxide become Fe ²⁺ at a high temperature to form pores, and calcium is dissolved to form pores. Steel sludge plays a role of foaming when heated, but when heated to high temperature, it reacts with calcium to become calcium wasteite (CaFe ₂ O ₄ ) crystals and turns black.

The amount of such steel sludge added is in the range of about 5 to 15% by weight, based on the total amount of the mixture. This is because if the addition amount thereof is less than 5% by weight, the addition effect is insignificant, and if the addition amount is more than 15% by weight, the black color of the resultant product is inferior and the commerciality is inferior. More preferably, it is in the range of about 8 to 12% by weight.

Clay is a mineral used to impart viscosity in the manufacture of products. Such clay components are preferably added in the range of about 5-15% by weight, based on the total amount of the mixture. If the added amount is less than 5% by weight, the viscosity is too low, and when heated to a high temperature, the rotary chel is broken in form and is discharged as powder.When used in excess of 15% by weight, the viscosity is too high and the manufacturing cost is too high. This is because the economic efficiency is lowered. More preferably, it is in the range of about 8 to 12% by weight.

Pearlite is a lightweight mineral and is used as a heat insulator or flame retardant. When minerals are put in a high pressure kiln and suddenly exposed to the atmosphere, the volume increases by about 10 times. The material obtained at this time is pearlite, but the material whose volume is increased by 10 times or less during the process is discarded without being used as a heat insulating material. The waste material thus discarded is waste pearlite, which has been almost left unused at present. This waste pearlite is a component for imparting lightness, so that the amount added is in the range of about 5 to 15% by weight based on the total amount of the mixture. This is because if the addition amount thereof is less than 5% by weight, the effect of addition is insignificant, and if it exceeds 15% by weight, the firing temperature rises, the strength of the lightweight aggregate obtained decreases, and the absorption rate increases. More preferably, it is in the range of about 8 to 12% by weight.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the Examples are not intended to limit or limit the present invention.

Experimental Example 1

First, the thermal characteristics of phosphate wastewater sludge were examined. X-ray diffraction analyzer and DTG Mass measurement results are shown in FIGS. 1A to 1E, 2 and 3 to confirm the thermal characteristics of phosphate wastewater sludge and the types of harmful gases generated during firing.

1A to 1E show X-ray diffraction diagrams of apatite crystals according to firing temperatures of phosphate wastewater sludge. That is, when the wastewater sludge was calcined at 100 ° C. (FIG. 1A), 300 ° C. (FIG. 1B), 500 ° C. (FIG. 1C), 700 ° C. (FIG. 1D), and 900 ° C. (FIG. 1E), the crystal formation of apatite was confirmed. It can be seen from the graph shown in Figure 1e that the crystal of apatite was completely produced at 900 ℃.

2 is a TGA (thermogravimetric analysis) result for confirming the weight loss with temperature while increasing the phosphate wastewater sludge to 900 ℃. The weight loss occurring near 118 ° C is the result of the evaporation of the attached moisture, and the weight loss occurring before 603 ° C is the weight loss that occurs as the nitrogen oxides (NO, NO ₂ ) contained in the sludge are decomposed. In order to confirm this more clearly, DTG (differential thermal analysis) results show two peaks between 20 and 30 minutes. This phenomenon generates the most gas between 20 and 30 minutes after heating. It can be seen that it rarely occurs.

FIG. 3 is a graph showing the results of measuring harmful gases with DTG Mass in order to confirm the type of gas generated between 20 and 30 minutes in FIG. 2. Through the graph, it can be seen that a large amount of gas having a molecular weight of 30 and 46 is leaked, and this gas is confirmed to be NO and NO ₂ , and almost no other harmful gas is generated. On the other hand, it is also confirmed that wastewater sludge contains a large amount of fluorine ions (F ⁻ ), but hardly occurs even when calcined at a high temperature.

<Examples 1 and 2>

Combining the raw materials under the following conditions, A combination is set to Example 1, B combination is set to Example 2, and then calcined to 1200 ° C. after drying, and then pulverized with Agate motar to 20 g of pH = 5. 100 ml of acidic water and 100 ml of distilled water were added and stirred for 30 minutes. In order to analyze the elution component contained in the filtrate by filtration, calcium ions were analyzed by using an atomic absorption spectrometer, and the anions were analyzed by ion exchange chromatography (Dionex).

(Combination ratio of raw materials for light aggregate production)

A combination: clay (10%), phosphate sludge (60%), steel sludge (10%), waste pearlite (10%), glaze sludge (10%)

B combination: clay (5%), phosphate sludge (60%), steel sludge (10%), waste pearlite (10%), glaze sludge (15%)

<Comparative Examples 1 and 2>

In the same manner as in Examples 1 and 2 described above, the C combination was set as Comparative Example 1, and the D combination was set as Comparative Example 2, with the combination of the raw materials as follows. The results analyzed in the same manner are shown in Table 1.

(Combination ratio of raw materials for light aggregate production)

C combination: clay (15%), phosphate sludge (60%), steel sludge (10%), waste pearlite (15%)

D combination: clay (15%), phosphate sludge (60%), steel sludge (10%), waste pearlite (12%), glaze sludge (3%)

Dissolution Characteristics of Lightweight Aggregate According to the Mixing Ratio of Raw Materials Combination F ^- NO ₃ ^- PO ₄ ^- Ca ²⁺ A 0 0 0 0 B 0 0 0 0 C 6.5 ppm 15 ppm 15 ppm 5.2 ppm D 1.5 ppm 6.5 ppm 2.8ppm 1.2 ppm

In the results shown in Table 1, it can be seen that the anion and calcium ion are not eluted at all in the C combination with 10% glaze sludge as a main component and the D combination with 15%. On the other hand, it can be seen that fluorine ions and calcium ions are eluted from the A combination without glaze sludge and the B combination with 3% glaze sludge.

This phenomenon is interpreted because Na, K, and Si contained in feldspar form glassy and react with fluorine to form Na ₂ SiF ₆ and K ₂ SiF ₆ , which are poorly soluble compounds, and are immobilized in the apatite crystal. .

<Example 3>

Manufacture of lightweight aggregate

When manufacturing artificial stone (stone) used for building and exterior of buildings as a substitute for natural stone, about 80% of aggregate such as foam cement, volcanic stone, and rubble is used to induce the weight reduction of artificial stone. It is not suitable because it degrades the coloring of artificial stone, and the volcanic stone is imported from a foreign country because the price is expensive, and rubble is not suitable because it is heavy. If the weight of the artificial stone is heavy, the fatigue of the building increases due to the load on the building, and the weight of the artificial stone should be lightened because the artificial stone can easily escape from the wall of the building and cause a safety accident.

In order to induce light weight by foaming the phosphate wastewater sludge discharged from silicon wafer, LCD, and semiconductor manufacturing process at high temperature, it is uniformly mixed in the following composition, followed by continuous drying process using the waste heat of rotary kill. It quickly calcined to 1,200 ° C within 1 hour to obtain a lightweight aggregate foamed to a volume of about 2 times or more. It is very easy to attach a drying device to the rotary killers to use the waste heat of the rotary killers when drying the mixture.

There are various methods to induce weight reduction, but the lightweight aggregate produced in this patent forms glassy at high temperature to reduce the absorption rate, plays a foaming role, and forms Na ₂ SiF ₆ , K ₂ SiF ₆ crystals to form F ⁻ Glaze sludge consisting of feldspar was added to prevent elution of ions.

And steel sludge was added so that oxygen generated when Fe ³⁺ ions contained in iron oxide became Fe ²⁺ at a high temperature to form pores, and calcium dissolved to form pores.

The combination ratio used to prepare the light weight aggregate was compared with the physical properties of the light weight aggregate and the inhibition of dissolution of harmful components, the combination of Table 1 was found to be the most ideal and adopted.

The glaze sludge used in this example was composed mostly of Feldspar, and the steel mill sludge contained about 60% iron and about 30% calcium.

The lightweight aggregate quickly fired at about 1200 ° C. high temperature was first pulverized using jaw crusher and then pulverized into 10 mm, 6 mm, and 3 mm sizes. The size is not particularly limited because it can be appropriately selected according to the type of product desired.

The light weight aggregate produced in this way was 2% absorbent, the elution of F ^- ion did not occur at all, and the specific gravity of the light weight aggregate measured by the Korea Institute of Building Materials is as follows.

Specific gravity according to the type of lightweight aggregate was as follows.

10 mm: 1.03, 6 mm: 1.10, 3 mm: 1.13

When manufacturing artificial stone, artificial stone was manufactured using lightweight aggregates of 10mm in size, 6mm in size, and 3mm in size, and the weight and colorability of artificial stone were almost the same as that of volcanic stone, and the manufacturing cost was reduced by about half.

As described above, according to the present invention, since the phosphate wastewater sludge is recycled and used for the production of lightweight aggregate, there is an effect of not only reducing the cost for waste disposal but also greatly reducing environmental pollution.

In addition, the manufactured lightweight aggregate has excellent properties of light weight, low absorption rate, high compressive strength, and harmful substances are not eluted, thereby making it possible to manufacture human-friendly building materials.

Although the present invention has been described above according to an embodiment of the present invention, it will be apparent to those skilled in the art that various modifications may be made without departing from the spirit of the present invention.

Claims (5)

Mixing from 20 to 60% by weight of a stabilizer comprising 40 to 60% by weight of phosphate wastewater sludge containing calcium, fluorine and phosphorus and glaze sludge containing feldspar, which can form apatite crystals; Calcining the resulting mixture in a temperature range of 900 to 1300 ° C; And Method for producing a lightweight aggregate comprising the step of pulverizing the resulting fired product. The stabilizer according to claim 1, wherein the stabilizer is based on the total amount of the mixture 5 to 15% by weight of glaze sludge, 5 to 15% by weight of calcium and iron components, 5 to 15% by weight of clay And 5 to 15% by weight of waste pearlite. The method of claim 1 further comprising the step of drying the mixture using waste heat of a rotary kill. The method of claim 1, wherein the fired material is milled to a size of 10mm, 6mm or 2mm. Light weight aggregate for construction and civil engineering made according to claim 1.